Microsoft Azure extension pack - Part 2 - Cluster support based on Event Hubs

[kaizimmerm]

Leverages Azure Event Hubs for Apache Kafka support for communication between cluster nodes. In addition I provided a rudimentary guide to deploy a cluster into Azure Kubernetes Service (AKS).

I do admit that these guides should go to the docs section in the homepage. However, I want to keep them here (in this PR) until the Boot 2 migration is complete.

Note: I had to upgrade to Spring Boot 2 in order to get the newest version of Spring Cloud Stream for the Kafka 1.0 support as required by Azure. So this PR depends on https://github.com/eclipse/hawkbit/pull/721

Boot 2 migration for the other modules needs to be done as well:. Here a quick status:

• AWS S3 module: seems to work (to be verified by some of the commiters that use AWS
• Azure modules: works
• MongoDB: needs migration. Looks a bit tricky. A few mandatory calls are not possible anymore with the new Spring data APIs.
• UAA: big breaks here on Spring side. I vote for letting this one go out of maintenance. None of the commiters uses the module. I can offer to provide a reference Azure Active Directory OAuth2 extension. Something I can actually maintain.

[kaizimmerm]

CQs are all "proceed with checkin" (see list that is part of the PR)